The invention relates to a control system and method for controlling fuel delivery to an internal combustion engine. More particularly, the invention relates to a control system and method that delivers one of two different fuel types to an engine capable of combusting either of the fuel types.
Powertrain controllers have long been used to control fuel delivery to engine cylinders. For engines having fuel injectors, the powertrain controllers have fuel injector drivers that generate control signals to control the amount of fuel delivered by the fuel injectors. In particular, the controller has one fuel injector driver for each fuel injector. Generally, the controller generates the control signals based on fuel maps that are stored in a memory of the controller.
Bi-fuel engines have been developed that can combust two or more different types of fuel. For example, bi-fuel engines have been developed that can combust (i) gasoline or (ii) alternate fuels such as compressed natural gas (CNG) or liquefied petroleum gas (LPG). Further, bi-fuel engines utilize two different types of fuel injectors, one type for delivering gasoline and a second type for delivering alternate fuels. Thus, for a four-cylinder bi-fuel engine, four fuel injectors (and corresponding drivers) would be utilized for delivering gasoline to the engine cylinders and four additional fuel injectors (and corresponding drivers) would be utilized for delivering an alternate fuel to the engine cylinders.
When designing bi-fuel engines, it is generally desirable to utilize as many pre-existing controllers and components as possible to reduce development costs and time. Thus, designers may use a previously designed powertrain controller for controlling gasoline fuel delivery in conjunction with an alternate fuel controller for controlling fuel delivery of an alternate fuel (AF). However, this approach raises the following problems. Generally, the alternate fuel controllers are designed by third party manufacturers and have substantially different control strategies for fuel delivery as compared to the powertrain controller. Thus, because different fuel control methodologies are utilized in both controllers, engine designers have increased difficulty meeting lower vehicle emission standards.
Engine designers have alternatively designed new powertrain controllers that can handle both the gasoline fuel delivery and alternate fuel delivery to a bi-fuel engine. In particular, new powertrain controllers have been designed having two sets of fuel injector drivers, one set for controlling gasoline fuel injectors and one set for controlling AF fuel injectors. However, the costs associated with designing new powertrain controllers having a predetermined number of gasoline and AF fuel injector drivers for each new bi-fuel engine is prohibitively expensive.
The above-identified disadvantages of conventional control systems are substantially overcome by a control system and method described and claimed herein.
The control system can control fuel delivery of two types of fuel to a bi-fuel engine. The two types of fuel may comprise any conventional fuel types that can be combusted in a bi-fuel engine. For example, a first fuel type may comprise either gasoline or diesel, and, a second fuel type may comprise CNG, LPG, or compressed hydrogen. The engine includes first and second fuel injectors for injecting first and second fuel types, respectively, into an engine cylinder. The control system includes a first controller (e.g., a powertrain controller) having a first driver generating a first signal indicative of a desired fueling amount for one of the first and second fuel types, respectively. The control system further includes a second controller (e.g., a bi-fuel controller) receiving the first signal. The second controller including second and third drivers for controlling the first and second fuel injectors, respectively. The second driver generating a second signal for controlling an amount of the first fuel type injected by the first fuel injector based on the first signal. The third driver generating a third signal for controlling an amount of the second fuel type injected by the second fuel injector into the cylinder based on the first signal. Generally, only one of the fuel types will be injected in the engine cylinders during a combustion cycle. It should be understood, however, that the control system is capable of injecting two fuel types into the engine cylinders during a combustion cycle.
A method of controlling an engine capable of combusting first and second fuel types in accordance with the present invention is provided. The engine having first and second fuel injectors for injecting the first and second fuel types, respectively, into an engine cylinder. The method includes generating a first signal indicative of a desired fueling amount for one of the first and second fuel types where the first signal is generated by a first controller (e.g., powertrain controller). The method further includes generating a second signal for controlling an amount of the first fuel type injected by the first fuel injector based on the first signal, when the first fuel type is to be combusted, where the second signal is generated by a second controller (e.g., bi-fuel controller).
The control system and method for controlling fuel delivery to a bi-fuel engine in accordance with the present invention provides a substantial advantage over conventional systems and methods. In particular, the control system provides a powertrain controller that generates control signals for either gasoline or AF fuel injectors, depending on which fuel type is desired to be combusted. Thus, a common control strategy can be utilized in a single controller to control both gasoline and AF fuel injection to meet regulated emission requirements and to improve fuel economy.
Utilizing the second simplified bi-fuel controller also results in substantial cost savings as compared to conventional alternate fuel controllers. As discussed above, the bi-fuel controller includes both gasoline and alternate fuel drivers that control the gasoline and AF fuel injectors based on control signals received from the powertrain controller. Thus, the complex calculations for fuel delivery are not performed in the bi-fuel controller resulting in decreased memory requirements and software complexity as compared to conventional alternate fuel controllers. Further, the bi-fuel controller can be implemented as a xe2x80x9cplug-inxe2x80x9d module to allow a powertrain controller to double the number of fuel injectors that can be controlled. For example, a powertrain controller having four fuel injector drivers could be utilized with the bi-fuel controller to control four gasoline fuel injectors and four alternate fuel injectors. Thus, an existing powertrain controller designed for controlling gasoline delivery to four engine cylinders, for example, could be adapted to control bi-fuel delivery to the cylinders without adding any additional hardware, except for the simplified bi-fuel controller.